Aeration:

Aeration is the process of providing oxygen from the atmosphere to effect beneficial changes in the raw water. Due to aeration undesirable gases such as carbon dioxide and hydrogen sulphide is liberated. The absorption and release of gases in water is a slow process. Hence, water is agitated or a great water area is exposed to the atmosphere. This is done by splashing water over trays to break up the stream into countless droplets or by reversing the effect and blowing air bubbles through water.